Science Questions

Do all plants have leaves?

The simplest types of plants, like algae, don't have leaves. But they do have chlorophyll in their cells and make their own food through photosynthesis, using sunlight, water, and minerals.

Mosses have leaf-like structures that carry out photosynthesis, but they are not true leaves because they don't have the special tissues-xylem and phloem-that distribute food, water, and minerals throughout most plants. The lack of a transportation system is the reason that mosses are so tiny and low to the ground.

More complex types of plants have leaves. Leaf shape is often determined by conditions in the environment. Usually, where sunlight and water are plentiful, leaves are flat and broad, providing a large surface area where photosynthesis can take place. Where weather is cold and dry, however, water loss can be a problem. The long, needle-shaped leaves of conifer trees (including pines), for example, help retain water, allowing the plants to grow in very dry, cold places, far north or high in the mountains. The extreme environment of the desert-intensely hot and dry-has brought about other special leaf adaptations. Many desert plants have fleshy leaves (and stems) in which they are able to store large amounts of water. Over millions of years the leaves of desert cactus plants became so small-to restrict water loss through transpiration-that on many only sharp spines remain. The thick-skinned stems or branches of cactus plants now do the job that leaves do for other plants, making food through photosynthesis.

Do all plants have roots?
The simplest types of plants don't have roots. Single-celled green algae, for instance, float on water surfaces, as do many types of seaweed, which are larger types of algae. Those seaweeds that do cling to the seabed do so through growths called "steadfasts," which are not true roots. Seaweed absorbs water and minerals from the sea through all its parts.

Similarly, simple plants like mosses form low-growing mats in damp places, soaking up the moisture they need directly from their environment. Instead of roots they have thread-like growths called rhizoids that anchor them to rocks or trees.

More complex forms of plants, though, like ferns, conifers (cone-bearing plants), and flowering plants, all have true roots and stems-an internal transportation system that can move water and minerals from their source to wherever they are needed.

Land plants have two types of roots: tap roots and fibrous roots. A plant's root type is often determined by its water source. A tap root is a large, single root that grows straight down to reach water deep in the soil (with smaller roots branching off of it). Fibrous roots have no main root but spread out in a wide web to gather water located in the top layers of soil. In places like rain forests-where there is abundant plant growth with little ground space for roots and plenty of moisture-some plants grow high up in trees. These epiphytes, or air plants, have fibrous, spongy, aerial roots that get moisture from the frequent rains and take minerals from the surface of the tree on which they grow (or from the plant debris that gathers around their roots). Many orchids are epiphytic plants.

(taken from http://www.answers.com/)

How plants prepare for winter?
http://www.sciencemadesimple.com/leaves.html

What organisms are Asexual?
http://qldscienceteachers.tripod.com/biology/08reproduction/01asexual_and_sexual_reproduction.pdf
How to keep bread from getting moldy?
http://www.ehow.com/how_4851950_keep-sandwich-bread-growing-mold.html#

Internal or External Fertilisation
Fish, Amphibians & Mollusks - External
[Except for guppy,shark, molly and swordtail are internal.
Primitive salamanders have external fertilization, but most have internal fertilization. All caecilians have internal fertilization]

- disadvantage - A strong wind or current may interfere with fertilization

Mammals, Birds & Reptiles - Internal